Output controller for controlling data output of a synchronous semiconductor memory device

ABSTRACT

An output controller includes: an output enable signal generator for generating corresponding ones among a plurality of output enable signals based on a preset column address strobe (CAS) latency, each of the output enable signals having information relating to a delay time from an activation timing of a CAS signal; and an output driving signal generator for receiving the plurality of output enable signals corresponding to the preset CAS latency and outputting rising and falling output driving signals for controlling an output timing of data.

FIELD OF THE INVENTION

The present invention relates to a semiconductor memory device, and moreparticularly to an output controller for controlling a data output of asemiconductor memory device.

DESCRIPTION OF RELATED ARTS

As semiconductor memory devices are highly integrated, many attemptshave been made to increase their operating speed. To achieve thispurpose, synchronous memory devices which operate in synchronizationwith an external clock have been introduced.

A single data rate (SDR) synchronous memory device inputs and outputsone data bit via one data pin in synchronization with a rising edge ofthe external clock during one clock cycle.

However, the SDR synchronous memory device is insufficient to satisfythe speed requirement of a high-speed system. Thus, a double data rate(DDR) synchronous memory device which processes two data bits during oneclock cycle has been proposed.

In the DDR synchronous memory device, two data bits are consecutivelyinput and output through data input/output pins in synchronization withrising and falling edges of the external clock. The DDR synchronousmemory device can implement at least two times the bandwidth of the SDRsynchronous memory device without increasing the frequency of the clock,thus obtaining the high-speed operation.

Because the DDR memory device has to receive or output two data bitsduring one clock cycle, a data access method employed in theconventional synchronous memory device can no longer be used.

If the clock cycle is about 10 ns, two consecutive data bits must besubstantially processed within about 6 nsec or less, except for therising time and the falling time (about 0.5×4=2 ns) and time necessaryfor meeting other specifications. However, it is difficult to performthe process within the memory device. Therefore, the memory deviceoperates in synchronization with the rising and falling edges of theclock only when inputting/outputting data from/to an external circuit.Substantially, the two data bits are processed in synchronization withone edge of the clock within the memory device.

In order to transfer data from a memory device to an internal coreregion or to output the transferred data to an external circuit, a newdata access method is required.

The synchronous memory device uses several concepts different from thoseof the asynchronous memory device. One of them is a CAS latency (CL).The CAS latency is the number of clocks that are counted from an inputof a read command to data output. If CL=3, it means that data are outputto an external circuit after three clock cycles from an input of theread command. The CAS latency determines data output timing. In aninitial operation of the semiconductor memory device, a detected set CLvalue is used to access and output data.

Therefore, a data output enable signal is generated after an operatingclock cycle is delayed as much as the set CAS latency. Also, when thedata output enable signal is activated, the accessed data is output inresponse to the read command.

The operating clock used is a delayed lock loop (DLL) clock obtained bydelay locking an external clock by a predetermined time. This DLL clockis generated from a delay locked loop (DLL) circuit. In the synchronoussemiconductor memory device, the data output has to be accuratelysynchronized with the rising and falling edges of the external clock.However, due to the delay time of the clock signal, which inevitablyoccurs during the internal processing, the data output cannot beaccurately synchronized with the rising and falling edges of theexternal clock.

FIG. 1 is a block diagram of a conventional data output unit foroutputting data corresponding to a read command in a DDR synchronizationmemory device.

The conventional data output unit includes an output enable signalgenerator 10 and an output driving signal generator 20. The outputenable signal generator 10 generates a plurality of output enablesignals OE00 to OE30 having information relating to a delay time from anactivation timing of a read column address strobe (CAS) signal CASP6_RD.The output driving signal generator 20 receives the plurality of outputenable signals OE00 to OE30 and generates rising and falling outputdriving signals ROUTEN and FOUTEN in response to CAS latency informationsignals CL1 to CL5.

For reference, the read CAS signal CASP6_RD is produced by a readoperation within the semiconductor memory device, and only the CASlatency information signals CL1 to CL5 corresponding to the CAS latencyare activated.

Although not shown in FIG. 1, the rising and falling output drivingsignals ROUTEN and FOUTEN control timing when data output from a memorycore block in response to the read command is output through a data pad.In order that the data output through the data pad satisfies the CASlatency, the rising and falling output driving signals ROUTEN and FOUTENshould be generated in consideration of the CAS latency. Accordingly,when the rising and falling output driving signals ROUTEN and FOUTEN aregenerated, the plurality of output enable signals OE00 to OE30 aregenerated in order to provide information relating to the CAS latency.

FIG. 2 is a block diagram of the output enable signal generator 10 shownin FIG. 1.

The output enable signal generator 10 includes an inverter chain 11 andfirst to third shifter registers 12, 13 and 14. The inverter chain 11delays and transfers the read CAS signal CASP6_RD. The first shiftregister 12 receives an output of the inverter chain 11 to output afirst output enable signal OE00 in response to a rising DLL clockRCLKDLL and a second output enable signal OE10 by delaying the outputsignal of the inverter chain 11 by one clock. The second shift register13 is initiated in response to an initial signal OE_RSTB and outputs athird output enable signal OE15 by delaying the second output enablesignal OE10 by half clock and a fourth output enable signal OE20 bydelaying the second output enable signal OE10 by one clock. The thirdshift register 14 is initiated in response to the initial signal OE_RSTBand outputs a fifth output enable signal OE25 by delaying the fourthoutput enable signal OE20 by half clock and a sixth output enable signalOE30 by delaying the fourth output enable signal OE20 by one clock.

FIG. 3 is a waveform diagram illustrating an operation of the outputenable signal generator 10 shown in FIG. 2.

The read CAS signal CASP6_RD is activated after a read command RD isapplied. After the read CAS signal CASP6_RD is activated, the outputenable signal generator 10 sequentially activates the first to sixthoutput enable signals OE00 to OE30 in units of half clock or one clockin response to the rising DLL clock RCLKDLL.

Hereinafter, referring to FIGS. 1 to 3, an operation of the conventionaldata output unit in the semiconductor memory device will be described.

First, if the read CAS signal CASP6_RD is activated after the readcommand RD0 is applied, the output enable signal generator 10sequentially activates the first to sixth output enable signals OE00 toOE30 in units of half clock or one clock in response to the rising DLLclock RCLKDLL.

The output driving signal generator 20 outputs the rising and fallingoutput driving signals ROUTEN and FOUTEN in response to activated onesamong the CAS latency information signals CL1 to CL5.

As described above, when the rising and falling output driving signalsROUTEN and FOUTEN are generated, some of the output enable signals OE00to OE30 may not be required.

Table 1 shows a corresponding one of the output enable signals, which isrequired according to the predetermined CAS latency.

TABLE 1 CL (CAS Latency) 0E 1 0E00 2 0E10 3 0E20 4 0E30 5 0E40 6 0E50

When the CAS latency is set to 1, the first output enable signal OE00 isonly used. When the CAS latency is set to 2, the first and second outputenable signals OE00 and OE10 are used. Likewise, when the CAS latency isset to 3, the first and third output enable signals OE00 and OE15 arerequired.

As described above, when the rising and falling output driving signalsROUTEN and FOUTEN are generated the number of required output enablesignals differs according to the predetermined CAS latency.

However, the conventional data output unit always generates all of theoutput enable signals even if they are not all required. As a result,unnecessary current consumption is occurs.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide anoutput controller for reducing unnecessary current consumption.

In accordance with an aspect of the present invention, there is providedan output controller including: an output enable signal generator forgenerating corresponding ones among a plurality of output enable signalsbased on a preset column address strobe (CAS) latency, each of theoutput enable signals having information relating to a delay time froman activation timing of a CAS signal; and an output driving signalgenerator for receiving the plurality of output enable signalscorresponding to the preset CAS latency and outputting rising andfalling output driving signals for controlling an output timing of data.

In accordance with another aspect of the present invention, there isprovided a semiconductor device for controlling data output timing,including: an initial synchronizing unit for outputting a first outputenable signal by synchronizing a read CAS signal with a rising DLLclock; first to fifth synchronizing units, connected in series, each forreceiving an output signal of the respective previous stage andoutputting a corresponding output enable signal when a correspondingcontrol signal is activated, wherein the first synchronizing unitreceives the first output enable signal; a control unit for receivingthe rising DLL clock and generating a plurality of control signalscorresponding to a preset CAS latency; and an output driving signalgenerator for receiving the output enable signals activated in responseto the rising DLL clock and outputting a rising driving signal inresponse to a corresponding CAS latency.

In accordance with further aspect of the present invention, there isprovided an output controller, including: an interval signal generatorfor generating a plurality of interval signals activated at regularintervals from activating a flag signal, and a control signal generatorfor outputting a plurality of control signals based on the plurality ofinterval signals, wherein an interval signal corresponding to anactivated selection signal among a plurality of selection signals isonly activated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the preferredembodiments given in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a block diagram of a conventional data output unit foroutputting data corresponding to a read command in a DDR SDRAM;

FIG. 2 is a block diagram of an output enable signal generator shown inFIG. 1;

FIG. 3 is a waveform diagram illustrating an operation of the outputenable signal generator shown in FIG. 2;

FIG. 4 is a block diagram of an output controller in accordance with anembodiment of the present invention;

FIG. 5 is a detailed circuit diagram of an output enable signalgenerator shown in FIG. 4 in accordance with a first embodiment of thepresent invention;

FIG. 6 is a detailed circuit diagram of an output enable signalgenerator shown in FIG. 4 in accordance with a second embodiment of thepresent invention; and

FIG. 7 is a circuit diagram of an output driving signal generator shownin FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

An output controller in accordance with exemplary embodiments of thepresent invention will be described in detail with reference to theaccompanying drawings.

FIG. 4 is a block diagram of an output controller in accordance with anembodiment of the present invention.

The output controller of the present invention includes an output enablesignal generator 100 and an output driving signal generator 200. Theoutput enable signal generator 100 generates corresponding ones among aplurality of output enable signals OE00 to OE50 having informationrelating to a delay time from an activation timing of a read columnaddress strobe (CAS) signal CASP6_RD based on CAS latency informationsignals CL1 to CL5. The output driving signal generator 200 receives theplurality of output enable signals OE00 to OE50 and generates rising andfalling output driving signals ROUTEN and FOUTEN in response to the CASlatency information signals CL1 to CL6.

FIG. 5 is a detailed circuit diagram of the output enable signalgenerator 100 shown in FIG. 4 in accordance with a first embodiment ofthe present invention. Particularly, FIG. 5 shows the output enablesignal generator 100 which is operated in synchronization with a risingdelay locked loop (DLL) clock RCLKDLL. The output enable signalgenerator 100 operated in synchronization with a falling DLL clockFCLKDLL is the same circuit structure shown in FIG. 5, except that theoutput enable signals are activated half clock later.

As shown, the output enable signal generator 100 includes an inverterchain 110, an initial synchronizing unit 120, a control unit 131 to 136,and first to fifth synchronizing units 141 to 145.

The inverter chain 110 delays and transfers the read CAS signal CASP6_RDto the initial synchronizing unit 120. The initial synchronizing unit120 outputs a first output enable signal OE00 by synchronizing an outputsignal of the inverter chain 110 with the rising DLL clock RCLKDLL. Thecontrol unit 131 to 136 receives the rising DLL clock RCLKDLL and theCAS latency information signals CL1 to CL5, and generates first to fifthcontrol signals. The first to fifth synchronizing units 141 to 145connected in series receive output signals of the respective previousstages and output the output enable signals when a corresponding controlsignal output from the control unit 131 to 136 is activated.

In detail, the initial synchronizing unit 120 includes a first transfergate TG1, a first inverter I1 and a first latch unit 122. The firsttransfer gate TG1 transfers an output of the inverter chain. 110 inresponse to a logic level ‘LOW’ of the rising DLL clock RCLKDLL. Thefirst inverter I1 inverts an output of the first transfer gate TG1. Thefirst latch unit 122 latches an output of the first inverter I1 andoutputs the latched signal as the first output enable signal OE00.

The control unit 131 to 136 includes an information expanding unit 131and first to fifth control signal generating units 132 to 136. Theinformation expanding unit 131 activates a first information expandingsignal CL12 when the first and second CAS latency information signalsCL1 and CL2 are inactivated, and activates a second informationexpanding signal CL34 when the third and fourth CAS latency informationsignals CL3 and CL4 are inactivated. The first control signal generatingunit 132 outputs the rising DLL clock RCLKDLL as a first control signalwhen the first CAS latency information signal CL1 is inactivated. Thesecond control signal generating unit 133 inverts the rising DLL clockRCLKDLL to output the inverted signal as a second control signal whenthe first information expanding signal CL12 is activated. The thirdcontrol signal generating unit 134 inverts the rising DLL clock RCLKDLLto output the inverted signal as a third control signal when the firstinformation expanding signal CL12 is activated and the third CAS latencyinformation signal CL3 is inactivated. The fourth control signalgenerating unit 135 inverts the rising DLL clock RCLKDLL to output theinverted signal as a fourth control signal when the first and secondinformation expanding signals CL12 and CL34 are activated. The fifthcontrol signal generating unit 136 inverts the rising DLL clock RCLKDLLto output the inverted signal as a fifth control signal when the firstand second information expanding signals CL12 and CL34 are activated andthe fifth CAS latency information signal CL5 is inactivated.

In detail, the information expanding unit 131 includes a first NOR gateNR1 and a second NOR gate NR2. The first NOR gate NR1 receives the firstand second CAS latency information signals CL1 and CL2 to output thefirst information expanding signal CL12. The second NOR gate NR2receives the third and fourth CAS latency information signals CL3 andCL4 to output the second information expanding signal CL34.

The first control signal generating unit 132 includes a third NOR gateNR3 which receives an inverted rising DLL clock RCLKDLLB and the firstCAS latency information signal CL1 to output the first control signal.

The second control signal generating unit 133 includes a first NAND gateND1 which receives the rising DLL clock RCLKDLL and the firstinformation expanding signal CL12 to output the second control signal.

The third control signal generating unit 134 includes a second inverterI2 and a second NAND gate ND2. The second inverter I2 inverts the thirdCAS latency information signal CL3. The second NAND gate ND2 receives anoutput of the second inverter I2, the rising DLL clock RCLKDLL and thefirst information expanding signal CL12 to output the third controlsignal.

The fourth control signal generating unit 135 includes a third NAND gateND3 which receives the first and second information expanding signalsCL12 and CL34 and the rising DLL clock RCLKDLL to output the fourthcontrol signal.

The fifth control signal generating unit 136 includes a third inverterI3 and a fourth NAND gate ND4. The third inverter I3 inverts the fifthCAS latency information signal CL5. The fourth NAND gate ND4 receives anoutput of the third inverter I3, the rising DLL clock RCLKDLL and thefirst and second information expanding signals CL12 and CL34 to outputthe fifth control signal.

The first synchronizing unit 141 includes a second transfer gate TG2 anda fourth inverter I4 and a second latch unit 141A. The second transfergate TG2 transfers the first output enable signal OE00 in response to alogic level ‘HIGH’ of the first control signal. The fourth inverter I4inverts an output of the second transfer gate TG2. The second latch unit144A latches an output of the fourth inverter I4 to output a secondoutput enable signal OE10.

The second to fifth synchronizing units 142 to 145 have the samestructures as that of the first synchronizing unit 141 except that theyoutput third to sixth control signals in response to a logic level ‘LOW’of each corresponding control signal.

For reference, if the CAS latency is set to 1, the first CAS latencyinformation signal CL1 is activated with a logic level ‘HIGH’ and if theCAS latency is set to 2, the second CAS latency information signal CL2is activated with a logic level ‘HIGH’. Likewise, if the CAS latency isset to 3, the third CAS latency information signal CL3 is activated witha logic level ‘HIGH’.

The first control signal is activated with a logic level ‘HIGH’ and thesecond to fifth control signals are activated with a logic level ‘LOW’.In addition, the first and second information expanding signals CL12 andCL34 are activated with a logic level ‘HIGH’.

Hereinafter, an operation of the output enable signal generator 100 willbe described in detail.

First, if the CAS latency is set to 1, the first CAS latency informationsignal CL1 is activated with a logic level ‘HIGH’ and the second tofifth CAS latency information signals CL2 to CL5 are inactivated with alogic level ‘LOW’.

The information expanding unit 131 inactivates the first informationexpanding signal CL12 with a logic level ‘LOW’ and activates the secondinformation expanding signal CL34 with a logic level ‘HIGH’.

The first control signal generating unit 132 outputs the first controlsignal with a logic level ‘LOW’ in response to the logic level ‘HIGH’ ofthe first CAS latency information signal CL1. Each of the second tofifth control signal generating units 133 to 136 outputs the second tofifth control signals with a logic level ‘HIGH’ in response to the logiclevel ‘LOW’ of the first information expanding signal CL12.

If the read CAS signal CASP6_RD is activated after the read command isapplied, the initial synchronizing unit 120 outputs the first outputenable signal OE00 in response to a logic level ‘LOW’ of the rising DLLclock RCLKDLL. The first to fifth synchronizing units 141 to 145 areturned-off in response to the first to fifth control signals.

Accordingly, when the read CAS signal CASP6_RD is activated, the firstoutput enable signal OE00 is only activated in response to the risingDLL clock RCLKDLL. The second to sixth output enable signals OE10 toOE50 are not activated.

Next, if the CAS latency is set to 3, the third CAS latency informationsignal CL3 is activated with a logic level ‘HIGH’ and the other CASlatency information signals CL1, CL2, CL4 and CL5 are inactivated with alogic level ‘LOW’.

The information expanding unit 131 inactivates the first informationexpanding signal CL12 with a logic level ‘HIGH’ and activates the secondinformation expanding signal CL34 with a logic level ‘LOW’.

The first control signal generating unit 132 outputs the first controlsignal by inverting the inverted rising DLL clock RCLKDLLB in responseto the logic level ‘LOW’ of the first CAS latency information signalCL1. The second control signal generating unit 133 outputs the secondcontrol signal by inverting the rising DLL clock. RCLKDLL in response tothe logic level ‘HIGH’ of the information expanding signal CL12. Each ofthe third to fifth control signal generating units 134 to 136 outputsthe corresponding control signal with a logic level ‘HIGH’ in responseto the logic level ‘HIGH’ of the third CAS latency information signalCL3 and the logic level ‘LOW’ of the second information expanding signalCL34.

If the read CAS signal CASP6_RD is activated after the read command isapplied, the initial synchronizing unit 120 outputs the first outputenable signal OE00 in response to a logic level ‘LOW’ of the rising DLLclock RCLKDLL. The first and second synchronizing units 141 and 142output the second and third output enable signals OE10 and OE20 inresponse to the first and second control signals. The third and fifthsynchronizing units 143 and 146 are turned-off in response to the thirdand fifth control signals.

Accordingly, after the read CAS signal CASP6_RD is activated, the firstto third output enable signals OE00 to OE20 are sequentially activatedin synchronization with the rising DLL clock RCLKDLL.

As described above, the output enable signal generator 100 in accordancewith the first embodiment of the claimed invention further includes thecontrol unit 131 to 136 receiving the CAS latency information signalsCL1 to CL5. As a result, each transfer gate provided in thesynchronizing units is turned off according to the control signalsoutput from the control unit 131 to 136. Accordingly, it is possible toreduce unnecessary current consumption by turning off the synchronizingunits which generates unnecessary output enable signals.

FIG. 6 is a circuit diagram of the output enable signal generator 100shown in FIG. 4 in accordance with a second embodiment of the presentinvention.

The output enable signal generator 100 in accordance with the secondembodiment of the present invention includes an inverter chain 150, aninitial synchronizing unit 155, a control unit 171 to 175, and first tofifth synchronizing units 161 to 165.

The inverter chain 150 delays and transfers the read CAS signal CASP6_RDto the initial synchronizing unit 155. The initial synchronizing unit155 outputs a first output enable signal OE00 by synchronizing an outputsignal of the inverter chain 150 with the rising DLL clock RCLKDLL. Thecontrol unit 171 to 175 receives an inverted rising DLL clock RCLKDLLBand the CAS latency information signals CL1 to CL5, and generates firstto fifth control signals. The first to fifth synchronizing units 161 to165 connected in series receive output signals of the respectiveprevious stages and output the output enable signals OE10 to OE50 when acorresponding control signal output from the control unit 171 to 175 isactivated.

In detail, the control unit includes first to fifth control signalgenerating units 171 to 175. Each of the first to fifth control signalgenerating units 171 to 175 outputs the rising DLL clock RCLKDLL as thefirst to fifth control signals when a corresponding one of the CASlatency information signals CL1 to CL5 is inactivated.

The second to fifth control signal generating units 172 to 175 have thesame structures as that of the first control signal generating unit 171except for the CAS latency information signal. The first control signalgenerating unit 171 is described as an exemplary structure.

The first control signal generating unit 171 includes a first NOR gateNR4 which receives the inverted rising DLL clock RCLKDLLB and a firstCAS latency information signal CL1 to output the first control signal.

If the CAS latency is set to 3, a third CAS latency information signalCL3 is activated with a logic level ‘HIGH’ and the other CAS latencyinformation signals CL1, CL2, CL4 and CL5 are inactivated with a logiclevel ‘LOW’.

The third control signal generating unit 173 outputs the third controlsignal with a logic level ‘LOW’. Each of the other control signalgenerating units 171, 172, 174 and 175 outputs the corresponding controlsignal by inverting the inverted rising DLL clock RCLKDLLB.

If the read CAS signal CASP6_RD is activated after the read command isapplied, the initial synchronizing unit 155 outputs the first outputenable signal OE00 in response to a logic level ‘LOW’ of the rising DLLclock RCLKDLL. The first and second synchronizing units 161 and 162sequentially output the second and third output enable signals OE10 andOE20 in units of one clock. At this time, the third synchronizing unit163 is turned off in response to the third control signal. Accordingly,though the fourth and fifth synchronizing units 164 and 165 are turnedon, they do not output and activate a corresponding control signal.

As described above, the output enable signal generator 100 in accordancewith the second embodiment of the claimed invention further includes thecontrol unit 171 to 175 which receives the CAS latency informationsignals CL1 to CL5 and controls the synchronizing units 161 and 165 forgenerating the output enable signals by synchronizing the read CASsignal CASP6_RD with the rising DLL clock RCLKDLL. That is, after therequired output enable signal is activated, the next synchronizing unitis only turned off in response to the preset CAS latency. As a result,the other synchronizing units which receive an output of the turned offsynchronizing unit do not activate the output enable signals. Forexample, if the CAS latency is set 2, the second synchronizing unit 162is turned off so that the required output enable signals, i.e., thefirst and second output enable signals OE00 and OE10, are onlyactivated. Likewise, if the CAS latency is set 4, the fourthsynchronizing unit 164 is turned off so that the required output enablesignals, i.e., the first to fourth output enable signals OE00 to OE30,are only activated.

The output enable signal generator 100 in accordance with the secondembodiment of the claimed invention may consume unnecessary currentgreater than that of the first embodiment because the next synchronizingunit is only turned off after the required output enable signal isactivated.

FIG. 7 is a circuit diagram of the output driving signal generator 200shown in FIG. 4.

The output driving signal generator 200 includes a first output drivingsignal generator 220 and a second output driving signal generator 240.The first output driving signal generator 220 receives correspondingoutput enable signals OE00 to OE50 to output the rising output drivingsignal ROUTEN in response to a corresponding signal among the first tosixth CAS latency information signals CL1 to CL6. The second outputdriving signal generator 240 receives corresponding output enablesignals OE05 to OE55 to output the falling output driving signal FOUTENin response to a corresponding signal among the first to sixth CASlatency information signals CL1 to CL6.

The first and second output driving signal generators 220 and 240include a plurality of transfer gates and a latch unit. Each of transfergates receives the output enable signal and transfers the receivedsignal in response to a corresponding. CAS latency information signal.The latch unit latches a signal at an output common node of the transfergates to output the latched signal as the rising output driving signalROUTEN or falling output driving signal FOUTEN.

The output enable signals OE00 to OE50 input to the first output drivingsignal generator 220 are activated in response to the rising DLL clockRCLKDLL, and the output enable signals OE05 to OE55 input to the secondoutput driving signal generator 240 are activated in response to thefalling DLL clock FCLKDLL.

Hereinafter, referring to FIGS. 4 to 7, the output controller of thepresent invention is described.

The output enable signal generator 100 selectively activates therequired output enable signal in response to the preset CAS latency. Theoutput driving signal generator 200 receives the output enable signalsand outputs the rising output driving signal ROUTEN and the fallingoutput driving signal FOUTEN based on the CAS latency informationsignals.

As described above, when the output enable signals are generated, theoutput controller of the claimed invention receives the CAS latencyinformation signals so as to generate the required output enable signalcorresponding to the CAS latency information signals. As a result, it ispossible to reduce unnecessary current consumption by preventingunnecessary output enable signals from being generated when the outputdriving signals are generated by the preset CAS latency

While the present invention has been described with respect to theoutput controller for controlling a data output timing by the readcommand, it is possible to apply the present invention to a block whichactivates a plurality of signals at regular intervals based on a flagsignal such as the read CAS signal and generates a control signalcorresponding to a selection signal. That is, when the plurality ofsignals are generated at regular intervals from the flag signal, it ispossible to reduce unnecessary current consumption by generating thecontrol signal based on the selection signal.

The present application contains a subject matter related to Koreanpatent application Nos. 2005-91570 & 2005-130483, filed in the KoreanIntellectual Property Office on Sep. 29, 2005 & Dec. 27, 2005,respectively, the entire contents of which are incorporated herein byreference.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

1. An output controller, comprising: an output enable signal generatorfor generating corresponding ones among a plurality of output enablesignals based on a preset column address strobe (CAS) latency, each ofthe output enable signals having information relating to a delay timefrom an activation timing of a read CAS signal; and an output drivingsignal generator for receiving the plurality of output enable signalscorresponding to the preset CAS latency and outputting rising andfalling output driving signals for controlling data output timing. 2.The output controller as recited in claim 1, wherein the output enablesignal generator includes: an initial synchronizing unit for outputtinga first output enable signal by synchronizing the read CAS signal with arising delay locked loop (DLL) clock; a control unit for receiving therising DLL clock and generating a plurality of control signalscorresponding to the preset CAS latency; and first to fifthsynchronizing units, connected in series, each for receiving an outputsignal of a previously connected synchronizing unit and outputting acorresponding output enable signal when a corresponding control signalis activated, wherein the first synchronizing unit receives the firstoutput enable signal.
 3. The output controller as recited in claim 2,wherein the initial synchronizing unit includes: a transfer gate fortransferring the read CAS signal in response to a second logic level ofthe rising DLL clock; an inverter for inverting an output of saidtransfer gate; and a latch unit for latching an output of said inverterand outputting the latched signal as the first output enable signal. 4.The output controller as recited in claim 3, wherein the control unitgenerates the plurality of control signals to selectively apply therising DLL clock to the first to fifth synchronizing units.
 5. Theoutput controller as recited in claim 4, wherein the control unitincludes: an information expanding unit for activating a firstinformation expanding signal when first and second CAS latencyinformation signals are inactivated, and activating a second informationexpanding signal when third and fourth CAS latency information signalsare inactivated; a first control signal generating unit for outputtingthe rising DLL clock as a first control signal when the first CASlatency information signal is inactivated; a second control signalgenerating unit for inverting the rising DLL clock to output theinverted signal as a second control signal when the first informationexpanding signal is activated; a third control signal generating unitfor inverting the rising DLL clock to output the inverted signal as athird control signal when the first information expanding signal isactivated and the third CAS latency information signal is inactivated; afourth control signal generating unit for inverting the rising DLL clockto output the inverted signal as a fourth control signal when the firstand second information expanding signals are activated; and a fifthcontrol signal generating unit for inverting the rising DLL clock tooutput the inverted signal as a fifth control signal when the first andsecond information expanding signals are activated and the fifth CASlatency information signal is inactivated.
 6. The output controller asrecited in claim 5, wherein the first synchronizing unit includes: atransfer gate for transferring the first output enable signal inresponse to a first logic level of the first control signal; an inverterfor inverting an output of said transfer gate; and a latch unit forlatching an output of said inverter to output a second output enablesignal.
 7. The output controller as recited in claim 6, wherein each ofthe second to fifth synchronizing units includes: a transfer gate fortransferring an output enable signal provided from a previouslyconnected synchronizing unit in response to a second logic level of acorresponding control signal; an inverter for inverting an output ofsaid transfer gate; and a latch unit for latching an output of saidinverter and outputting a corresponding output enable signal.
 8. Theoutput controller as recited in claim 7, wherein the informationexpanding unit includes: a first NOR gate for receiving the first andsecond CAS latency information signals to output the first informationexpanding signal; and a second NOR gate for receiving the third andfourth CAS latency information signals to output the second informationexpanding signal.
 9. The output controller as recited in claim 7,wherein the first control signal generating unit includes a NOR gate forreceiving an inverted rising DLL clock and the first CAS latencyinformation signal to output the first control signal.
 10. The outputcontroller as recited in claim 7, wherein the second control signalgenerating unit includes a NAND gate for receiving the rising DLL clockand the first information expanding signal to output the second controlsignal.
 11. The output controller as recited in claim 7, wherein thethird control signal generating unit includes: an inverter for invertingthe third CAS latency information signal; and a NAND gate for receivingan output of said inverter, the rising DLL clock and the firstinformation expanding signal to output the third control signal.
 12. Theoutput controller as recited in claim 7, wherein the fourth controlsignal generating unit includes a NAND gate which receives the first andsecond information expanding signals and the rising DLL clock to outputthe fourth control signal.
 13. The output controller as recited in claim7, wherein the fifth control signal generating unit includes: aninverter for inverting the fifth CAS latency information signal; and aNAND gate for receiving an output of said inverter, the rising DLL clockand the first and second information expanding signals to output thefifth control signal.
 14. The output controller as recited in claim 3,the control unit generates the plurality of control signals selectivelyactivated to turn on only a synchronizing unit that generates an outputenable signal corresponding to the preset CAS latency.
 15. The outputcontroller as recited in claim 14, wherein the control unit includesfirst to fifth control signal generating units, each for outputting therising DLL clock as first to fifth control signals when a correspondingCAS latency information signal is inactivated.
 16. The output controlleras recited in claim 15, wherein each of the first to fifth controlsignal generating units includes a NOR gate for receiving an invertedrising DLL clock and the corresponding CAS latency information signal tooutput a corresponding control signal.
 17. The output controller asrecited in claim 15, wherein each of the first to fifth synchronizingunits includes: a transfer gate for transferring the output signal ofthe previously connected synchronizing unit in response to a first logiclevel of the corresponding control signal among the first to fifthcontrol signals; an inverter for inverting an output of said transfergate; and a second latch unit for latching an output of said inverter tooutput the corresponding output enable signal.
 18. The output controlleras recited in claim 2, wherein the output driving signal generatorincludes: a first output driving signal generator for receiving theoutput enable signals to output the rising output driving signal inresponse to a corresponding CAS latency; and a second output drivingsignal generator for receiving the output enable signals to output thefalling output driving signal in response to the corresponding CASlatency, wherein the output enable signals input to the first outputdriving signal generator are activated in response to the rising DLLclock, and the output enable signals input to the second output drivingsignal generator are activated in response to the falling DLL clock. 19.The output controller as recited in claim 18, wherein each of the firstand second output driving signal generators includes: a plurality oftransfer gates, each for receiving and transferring a correspondingoutput enable signal in response to the corresponding CAS latency; and alatch unit for latching a signal at a common output node of the transfergates to output the latched signal as the rising or falling outputdriving signal.
 20. A semiconductor device for controlling a data outputtiming, comprising: an initial synchronizing unit for outputting a firstoutput enable signal by synchronizing a read CAS signal with a risingDLL clock; first to fifth synchronizing units, connected in series, eachfor receiving an output signal of the respective previous stage andoutputting a corresponding output enable signal when a correspondingcontrol signal is activated, wherein the first synchronizing unitreceives the first output enable signal; a control unit for receivingthe rising DLL clock and generating a plurality of control signalscorresponding to a preset CAS latency; and an output driving signalgenerator for receiving the output enable signals activated in responseto the rising DLL clock and outputting a rising driving signal inresponse to a corresponding CAS latency.
 21. The semiconductor device asrecited in claim 20, wherein the initial synchronizing unit includes: atransfer gate for transferring the read CAS signal in response to asecond logic level of the rising DLL clock; an inverter for inverting anoutput of said transfer gate; and a latch unit for latching an output ofsaid inverter and outputting the latched signal as the first outputenable signal.
 22. The semiconductor device as recited in claim 21,wherein the control unit includes: an information expanding unit foractivating a first information expanding signal when first and secondCAS latency information signals are inactivated, and activating a secondinformation expanding signal when third and fourth CAS latencyinformation signals are inactivated; a first control signal generatingunit for outputting the rising DLL clock as a first control signal whenthe first CAS latency information signal is inactivated; a secondcontrol signal generating unit for inverting the rising DLL clock tooutput the inverted signal as a second control signal when the firstinformation expanding signal is activated; a third control signalgenerating unit for inverting the rising DLL clock to output theinverted signal as a third control signal when the first informationexpanding signal is activated and the third CAS latency informationsignal is inactivated; a fourth control signal generating unit forinverting the rising DLL clock to output the inverted signal as a fourthcontrol signal when the first and second information expanding signalsare activated; and a fifth control signal generating unit for invertingthe rising DLL clock to output the inverted signal as a fifth controlsignal when the first and second information expanding signals areactivated and the fifth CAS latency information signal is inactivated.23. The semiconductor device as recited in claim 21, wherein the controlunit includes first to fifth control signal generating units, each foroutputting the rising DLL clock as first to fifth control signals when acorresponding CAS latency information signal is inactivated.
 24. Thesemiconductor device as recited in claim 23, wherein each of the firstto fifth control signal generating units includes a NOR gate forreceiving an inverted rising DLL clock and the corresponding CAS latencyinformation signal to output the corresponding control signal.